MECHANODESTRUCTION OF ISOPRENE RUBBER. PART 3. KINETICS OF OXIDATIVE DESTRUCTION

Continuation of studies of changes in molecular parameters, in particular, the molecular weight (MM) during the plasticization (P) of SKI-3 isoprene rubber. The kinetics of oxidative destruction (OD) in the temperature range (T) 30-130 °C and time (t) 30–600 s were studied in detail. Plasticization of rubber, as before, was carried out in a laboratory rubber mixer of the company «NFM», and gel chromatographic studies were carried out on a gel chromatograph of the company «Waters». The speed constant OD K0 decreases in absolute value with a decrease in T and an increase in t. The calculated effective activation energy of OD Eeff decreases from 24,4 to 13 kJ/mol in the studied t range. The influence of the oxygen diffusion process on the kinetic features of the OD of SKI-3 at Р is pointed out.

Investigation of the Deformation and Strength Properties of Elastomeric Compositions with Urea-Based Additives

The effect of blocked diisocyanates on the elastic-strength properties of elastomeric compositions based on SKI-3 isoprene rubber has been investigated. The synthesized additives are 2-isocyanato-4-phenylcarbamidotoluene (IPCT) and 2,4-diphenylcarbamidotoluene (DPCT). Tests were carried out to determine the physical and mechanical (conditional tensile strength, elongation at break, hardness) properties depending on the type and dosage of additives. It was found that samples with synthesized additives have strength and elongation at break higher than those of a sample without additives by 30 % and 200 %, respectively. There was also an increase in the tear resistance of all samples compared to the control (from 49.9 to 81.9 kN/m). An assumption is made about the formation of a network of physical connections, which provides an increase in these indicators. TMA analysis results showed a wider temperature range for reversible deformations (up to 180 °С).

Effect of the Epoxide Contents of Liquid Isoprene Rubber as a Processing Aid on the Properties of Silica-filled Natural Rubber Compounds

In this study, we examined the feasibility of using epoxidized liquid isoprene rubber (E-LqIR) as a processing aid for truck and bus radial (TBR) tire treads and investigated the effects of the epoxide content on the wear resistance, fuel efficiency, and resistance to extraction of the E-LqIRs. The results confirmed that, compared to the treated distillate aromatic extract (TDAE) oil, the E-LqIRs could enhance the filler–rubber interactions and reduce the oil migration. However, the consumption of sulfur by the E-LqIRs resulted in a lower crosslink density compared to that of the TDAE oil, and the higher epoxide content decreased the wear resistance and fuel efficiency because of the increased glass-transition temperature (Tg). In contrast, the E-LqIR with a low epoxide content of 6 mol% had no significant effect on the Tg of the final compound and resulted in superior wear resistance and fuel efficiency, compared to those shown by TDAE oil, because of the higher filler–rubber interactions.

A simple and green approach to the preparation of super tough IIR/SWCNTs nanocomposites with tunable and strain responsive electrical conductivity

Nanocomposites of single-wall carbon nanotubes in isobutylene isoprene rubber (IIR/SWCNTs) were successfully prepared by a simple and green wet process. The traditional melt mixing process and organic solvent dissolution suffered from unable to effectively disperse the SWCNTs of tangled structure, and degradation of polymer molecules, respectively. Our process very well avoided these two problems. The SWCNTs aqueous solutions emulsified by polyoxyethylene octyl phenol ether (OP-10) were firstly mixed and compounded with IIR rubber at a relatively high temperature, followed by the second step of melt compounding process with the addition of cross-linking agent and accelerators. The SWCNTs were dispersed uniformly, and a fine network was constructed in the matrix of the obtained IIR/SWCNTs nanocomposite with a low percolation threshold. With the concentration of SWCNTs as low as 2 phr, the IIR/SWCNTs nanocomposite received an electrical conductivity of 10−6∼10−3 S/cm, and a 71% improvement of tensile strength. By varying the loadings of SWCNTs in a certain range, the tensile strength, electrical conductivity, and dielectric property were found tunable. Besides, the nanocomposites also presented strain responsive specific resistance, excellent elongation (600–740%), and better heat resistance.

RESEARCH of ELASTOMERS properties BASED ON COMBINATION OF ISOPRENE AND NITRILE BUTADIENE RUBBERS

Применение резинотехнических изделий в крайних условиях Севера ставит ряд научно-технических проблем, связанных с их надежностью и безотказностью. Основной причиной выхода из строя техники вовремя эксплуатации при низких отрицательных температурах является потеря работоспособности уплотнительных резин по причине низкой морозостойкости. Одним из способов решения данной проблемы является разработка резиновых смесей на основе двух или более каучуков, обладающих высокимизначениями морозо- и агрессиво- стойкости. В работе приведены результаты исследования эластомеров на основе комбинации изопренового каучука марки СКИ-3 и бутадиен-нитрильного каучука марки БНКС-18. В результате проведённых исследований установлено, что при разных соотношениях каучуков СКИ-3 и БНКС-18 в резиновой смеси происходит изменение упруго-прочностных свойств эластомеров, стойкости к углеводородным средам, модуля упругости, твердости, плотности, остаточной деформации сжатия и износостойкости. При исследовании на дифференциально-сканирующем калориметре были выявлены две температуры стеклования у резин на основе комбинации каучуков. При помощи электронного микроскопа были получены снимки в объеме образцов, на которых наблюдается фазовая морфология резин, которая в зависимости от соотношения каучуков в смеси более характерна для бутадиен-нитрильного или изопренового каучуков. Также отмечено, что поверхность трения резины на основе БНКС-18 обладает наиболее шероховатойструктурой по сравнению с резиной с большим содержанием каучука СКИ-3. The use of rubber products in the extreme conditions of the North creates a number of scientific and technical problems associated with their trustworthiness and reliability. The main reason of equipment failure during operation at low negative temperatures is the performance loss of sealing rubbers due to low frost resistance. One of the ways to solve this problem is the development of rubber compounds based on two or more types of rubber with high values ​​of frost and aggression resistance. This article presents research results of elastomers based on a combination of isoprene rubber IR and nitrile butadiene rubber NBR. As a result, it was discovered that at different ratios of IR and NBR rubbers in a rubber compound, there is a change in the elastic-strength properties of elastomers, resistance to hydrocarbon media, elastic modulus, hardness, density, residual compression deformation and wear resistance. In the research of differential scanning calorimeter, two glass transition temperatures were identified as rubbers based on a combination of rubber. Using electronic microscope, images were obtained in the volume of samples, which is the phase morphology of rubbers is observed, which is depending on ratio of rubber in the mixture is more specific for nitrile butadiene or isoprene rubber. It was also noted that the friction surface of rubber based on NBR has the roughest structure compared to rubber with a high content of IR rubber.